Scottish National Dictionary (1700–)

1. The scorched stem of heather which remains after the smaller twigs are burnt.
Abd. 1790 A. ShirrefsGloss. 3; WatsonW.-B.: Birns, roots of burnt heath; or rather, the stronger stems of the heath that remain after the smaller twigs are gone.em.Sc. 1920 J. BlackAirtin' Hame 141: Meal and water were well stirred with some handy heather “birn,” and partaken of with keen relish by the thankful wayfarer.Lth. 1819 J. ThomsonPoems 37: Threescore o' bobbins, ten o' pirns, An auld blunt ax for hackin' birns.Gall.(D) 1901 TrotterGall. Gossip 192: The next time he saw her she was . . . tryin tae roast a half herrin on the heather birns amang the asse.Dmf. 1899 J. ShawCountry Schoolmaster 344: It is said of a niggardly frugal person, “It's a queer brae that he couldna get a bern off.”

2. A burnt mark, a brand on parts of the bodies of animals for identification of ownership.
Sc. 1725 RamsayGentle Shepherd Act III. Sc. ii. in Poems (1728) II.: Fourscore of breeding Ews of my ain Birn, Five Ky that at ae Milkin fills a Kirn, I'll gi'e to Peggy that Day she's a Bride.Sc. 1820 ScottMonastery ix.: I have left him [a fat bullock] in the upper cleugh as . . . he is marked both with cut and birn.Rxb. 1923 WatsonW.-B. 56: Birn. An identification mark on sheep, made by burning.